Phenyl(acyloxy)fluorosilanes C6H5Si(OCOR) nF3-n (n = 1, 2) and Phenyl(acyloxy)fluorochlorosilanes C6H5Si(OCOR)FCl

Article abstract of DOI:10.1134/S1070363211120103

The method of synthesis of the hitherto unknown class of organosilicon compounds, phenyl- (acyloxy)fluorosilanes C₆H₅Si(OCOR) _nF_3-n (n = 1, 2) and phenyl(acyloxy)fluorochlorosilanes C₆H₅Si(OCOR) FCl in up to 91% yield has been developed based on the reaction of phenyl(fluoro)chlorosilanes C₆H ₅SiCl_nF_3-n (n = 1, 2) with trimethylsilyl esters of carboxylic acids Me₃SiOC(O)R [R = H, CH₃, CF₃, CCl₃, ClCH₂, BrCH₂, CH ₂=CHCH₃, CH₂=CHPh, CH(CH₃)=CH ₂, Ph]. Pleiades Publishing, Ltd., 2011.

Full text of DOI:10.1134/S1070363211120103

ISSN 1070-3632, Russian Journal of General Chemistry, 2011, Vol. 81, No. 12, pp. 2487–2489. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © S.V. Basenko, L.E. Zelenkov, M.G. Voronkov, A.I. Albanov, D.А. Shabalin, 2011, published in Zhurnal Obshchei Khimii, 2011,
Vol. 81, No. 12, pp. 2039–2042.
Phenyl(acyloxy)fluorosilanes C6H5Si(OCOR)nF3–n (n = 1, 2)
and Phenyl(acyloxy)fluorochlorosilanes C6H5Si(OCOR)FCl
S. V. Basenko, L. E. Zelenkov, M. G. Voronkov, A. I. Albanov, and D. А. Shabalin
Favorskii Irkutsk Institute of Chemistry, Siberian Branch, Russian Academy of Sciences,
ul. Favorskogo, 1, Irkutsk, 664033 Russia
е-mail: sv_basenko@irioch.irk.ru
Received March 22, 2011
Abstract—The method of synthesis of the hitherto unknown class of organosilicon compounds, phenyl-
(acyloxy)fluorosilanes C6H5Si(OCOR)nF3–n (n = 1, 2) and phenyl(acyloxy)fluorochlorosilanes C6H5Si(OCOR)
FCl in up to 91% yield has been developed based on the reaction of phenyl(fluoro)chlorosilanes C6H5SiClnF3–n
(n = 1, 2) with trimethylsilyl esters of carboxylic acids Ме3SiOC(O)R [R = H, CH3, CF3, CCl3, ClCH2, BrCH2,
CH2=CHCH3, CH2=CHPh, CH(CH3)=CH2, Ph].
DOI: 10.1134/S1070363211120103
Phenyl(fluoro)chlorosilanes, PhSiF3–nCln [n = 1 (I),
2 (II)] are known to react with trimethylacetoxysilane
even at room temperature to form the earlier unknown
phenyl(acetoxy)difluoro- and phenyl(diacetoxy)fluoro-
silanes in a quantitative yield [1]. It was also found that
phenyltrifluorosilane behaves differently, and upon
reflux for 7–14 h did not split the Si–O–C group in tri-
methylacyloxysilanes. However, phenyl(aciloxy)difluoro-
silanes are formed at keeping the reaction mixture for
2–4 weeks at 20°С, although in a very low yield (<5–8%).
Carrying out the latter reaction with the molar ratio
of the reagents of 1:1 at 20°С over 2–3 h leads mainly
to the earlier unknown phenyl(acyloxy)fluoro-
chlorosilanes possessing a chiral silicon atom. Phenyl-
(diacyloxy)fluorosilanes have also been identified.
PhSiFCl2 + RC(O)OSiMe3
→ PhSiFClOC(O)R + PhSiF[OC(O)R]2 + Me3SiCl.
Low-boiling trimethylchlorosilane formed in these
reactions is easily removed from the reaction mixture
by distillation.
In continuation of the investigation of reactions of
phenyl(fluoro)chlorosilanes with trimethyl(acyloxy)
silanes we have developed a preparative method of the
synthesis of phenyl(acyloxy)fluorosilanes C6H5Si·
(OCOR)nF3–n [R = H, CH3, CF3, CCl3, ClCH2, BrCH2,
CH2=CHCH3, CH2=CHPh, CH(CH3)=CH2, Ph]) in 60–
91% yield. Thus, the reaction of phenyl(difluoro)-
chlorosilane with trimethyl(acyloxy)silanes (molar
ratio 1:1, 20°С, 0.5–1 h) affords phenyl(acyloxy)di-
fluorosilanes, whereas in the reaction of phenyl(fluoro)-
dichlorosilane with trimethyl(acyloxy)silanes with the
molar ratio 1:2 at 20°С for 7–8 h only phenyl(di-
acyloxy)fluoroilanes are formed.
From the GLC and 19F NMR spectroscopy data, the
rate of the reaction is determined by the number of
chlorine atoms (n) in the starting phenyl(fluoro)
chlorosilanes I and II, and it decreases in the series of
compounds PhSiF2Cl > PhSiFCl2 >PhSiCl3. This is
indicative of an increased ionic character of the Si–Cl
bond in PhSiF2Cl due to the presence of two fluorine
atoms in the molecule.
The yield of the products depends on the nature of
the acyloxy group in the starting trimethyl(acyloxy)-
silanes. In the reaction of PhSiF2Cl with Me3SiOCOR
(R = Me, Ph, CH2Br, H, CH2Cl, CCl3, CF3) with the
molar ratio 1:1 at 20°С the yield of the products after
52 h amounts to 92, 90, 76, 70, 61, 45, and 40%,
respectively. The decrease in the yield is apparently
due to the decrease in the nucleophilicity of the
acyloxy group with the increase of electronegativity of
substituent R in this order.
PhSiF3−nCln + n RC(O)OSiMe3
n = 2
n = 1
PhSiF[OC(O)R]2 + 2 Me3SiCl
PhSiF2OC(O)R + Me3SiCl
2487

2488
BASENKO et al.
Yields, 19F, 29Si NMR spectral parameters of phenyl(acyloxy)fluorosilanes (CCl4, 20 v/v%, 20°С), and pKa values of acids
RCOOH
PhSiHlg2OC(O)R
PhSiF2OC(O)H
Yield, %
69.7
pKa RCOOH
δSi, ppm
δF, ppm
JSiF, Hz
3.45
–65.6
–140.07
271.2
PhSiF2OC(O)CH3
91.2
–
4.75
5.05
4.19
2.85
2.90
0.70
0.23
4.66
4.69
4.44
3.45
4.75
5.05
4.19
2.85
2.90
0.70
0.23
4.66
–65.9
–
–141.07
–141.10
–140.62
–140.49
–140.59
–140.19
–139.96
–140.90
–140.71
–140.67
–128.55
–129.98
–130.09
–129.61
–129.30
–129.30
–128.39
–128.57
–129.81
268.5
–
PhSiF2OC(O)C(CH3)3
PhSiF2OC(O)Ph
89.8
61.2
75.6
45.3
40.1
74.0
73.3
73.0
44.1
44.2
–
–64.5
–66.0
–66.1
–66.2
–66.0
–65.1
–64.9
–64.8
–39.3
–39.8
–
268.6
272.0
271.5
276.4
276.6
268.0
266.9
267.4
298.7
296.4
–
PhSiF2OC(O)CH2Cl
PhSiF2OC(O)CH2Br
PhSiF2OC(O)CCl3
PhSiF2OC(O)CF3
PhSiF2OC(O)CCH3=CH2
(E)-PhSiF2OC(O)CH=CHCH3
(E)-PhSiF2OC(O)CH=CHPh
PhSiFClOC(O)H
PhSiFClOC(O)CH3
PhSiFClOC(O)C(CH3)3
PhSiFClOC(O)Ph
35.7
40.1
36.3
27.0
19.9
58.7
–38.2
–39.2
–39.3
–38.4
–38.0
–38.9
296.0
298.7
298.7
304.0
303.4
295.4
PhSiFClOC(O)CH2Cl
PhSiFClOC(O)CH2Br
PhSiFClOC(O)CCl3
PhSiFClOC(O)CF3
PhSiFClOC(O)CCH3=CH2
(E)-PhSiFClOC(O)CH=CHCH3
(E)-PhSiFClOC(O)CH=CHPh
PhSiF(OC(O)H)2
40.7
40.1
75.8
92.1
81.2
72.3
73.4
41.9
75.1
71.2
71.2
4.69
4.44
3.45
4.75
4.19
2.85
2.90
0.70
4.66
4.69
4.44
–38.9
–38.7
–61.7
–62.9
–59.9
–62.5
–62.5
–61.4
–61.3
–61.1
–60.8
–129.83
–129.75
–140.72
–142.21
–141.70
–141.43
–141.51
–140.69
–142.06
–142.04
–141.75
294.9
294.5
274.3
270.0
270.0
275.5
275.5
265.0
269.3
268.2
269.0
PhSiF[OC(O)CH3]2
PhSiF[OC(O)Ph]2
PhSiF[OC(O)CH2Cl]2
PhSiF[OC(O)CH2Br]2
PhSiF[OC(O)CCl3]2
PhSiF[OC(O)CCH3=CH2]2
(E)-PhSiF[OC(O)CH=CHCH3]2
(E)-PhSiF[OC(O)CH=CHPh]2
Yields, parameters of NMR spectra of phenyl(acyl-
oxy)fluorosilanes, and pKa values of the corresponding
acids are given in the table.
similar conditions the yield of the formed phenyl(acyl-
oxy)fluorosilanes is practically identical (73–74%), in
agreement with their pKa values (4.66; 4.69; 4.44).
In the reaction of PhSiF2Cl with trimethylsilyl
esters of α,β-unsaturated carboxylic acids Me3SiOCOR
[R = C(Me)=CH2, CH=CHMe, CH=CHPh] under
In the reaction of PhSiFCl2 with Me3SiOCOR [R =
C(Me)=CH2, H, CH=CHMe, CH=CHPh, CH2Cl, Ph,
CH2Br, CCl3] with the molar ratio of the reagents 1:1
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 81 No. 12 2011

PHENYL(ACYLOXY)FLUOROSILANES C6H5Si(OCOR)nF3–n (n = 1, 2)
2489
at 20°С phenyl(diacyloxy)fluorosilanes were identified.
Trimethylsilyl ester of trifluoroacetic acid does not
acylate phenyl(fluoro)dichlorosilane.
Earlier a reciprocal relationship between the value
of JSiF and electronegativity of the substituent was
suggested [3–4]. However, the values of JSiF in the
series of the obtained compounds do not obey this
relationship since the largest coupling constant is
observed for acyloxyfluorochlorosilanes rather than
diacyloxyfluorosilanes.
In the reactions with trimethyl(pivaloyloxy)silane,
acyloxysilanes C6H5Si(OCOCMe3)F2 and C6H5Si·
(OCOCMe3)FCl are formed only in trace amounts, and
the products of substitution of two chlorine atoms in
PhSiFCl2 were not detected, although pivalic acid is
weaker than acetic acid (pKa 5.05 and 4.75,
respectively). Therefore the rate and the course of the
reaction are affected not only by electronegativity but
also by the volume of substituent R since the values of
Es for R = Me and CMe3 are equal to 0.00 and –1.54,
respectively.
EXPERIMENTAL
1H, 19F, 29Si NMR spectra were recorded on a
Bruker DPX 400 (400 MHz) instrument in CCl4,
internal reference for 1H, 29Si TMS, for 19F CFCl3.
Mixed phenyl(chloro)fluorosilanes C6H5SiClnF3–n
(n = 1–2) were obtained by conproportionation of
PhSiF3 with PhSiСl3 [5]. Trimethylsilyl esters of the
corresponding acids were obtained by the known
procedure [6].
Ph
O
CH3
F
Si
F
O
CH3
CH3
Cl
R
Reaction of phenyl(chloro)difluorosilane with tri-
methylacetoxysilane. The mixture of 1.8 g (0.01 mol)
of phenyl(chloro)difluorosilane and 1.3 g (0.01 mol) of
trimethylacetoxysilane was kept at room temperature
for 15–30 min. The formed trimethylchlorosilane was
distilled off under reduced pressure (10 mm Hg), the
Si
The mechanism of the studied reactions apparently
includes the formation of the transition state in which
the silicon atom is pentacoordinate.
1
residue was analyzed by H, 19F and 29Si NMR
The synthesized phenyl(acyloxy)difluorosilanes
disproportionate after long standing at room tempera-
ture or at heating. The effect of the nature of the alkyl
or haloalkyl substituent R on the rate of this reaction is
negligible. Phenyl(diacyloxy)fluorosilanes are more
stable and only partly disproportionate at the vacuum
distillation.
spectroscopy (see the table).
The reactions of phenyl(chloro)difluorosilane and
phenyl(dichloro)fluorosilane with trimethylsilyl esters
of carboxylic acids Ме3SiOCOR [R = H, CH3, CF3,
CCl3, ClCH2, BrCH2, CH2=CHCH3, CH2=CHPh,
CH(CH3)=CH2, Ph] were performed similarly (see the
table). The obtained compounds are very sensitive to
heating and air moisture.
The structure of all synthesized compounds is proved
by the data of 1H, 13C, 19F, 29Si NMR spectroscopy.
REFERENCES
As in the case of phenyl(alkoxy)fluorosilanes
PhSi(OR)nF3–n [2], the replacement of the fluorine
atoms by acyloxy group [PhSiF2OAc→PhSiF(OAc)2]
also results in some shielding of the silicon atom (by
3–5 ppm) and shielding of the fluorine atom (by
~1 ppm), and to the increase in the coupling constant
(29Si–19F) by 1–11 Hz. These changes of the NMR
parameters are parallel to those caused by the decrease
in the contribution of the intra– and intermolecular
interactions F–Si←O=C in going from difluorides to
monofluorides.
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Albanov, A.I., and Gebel, I.A., Russ. J. Gen. Chem.,
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The replacement of the fluorine atom of phenyl-
(acyloxy)difluorosilane by chlorine atom expectedly
results in strong deshielding of the silicon atom (25–
27 ppm), fluorine atom (11 ppm) and the increase in
the coupling constant 29Si–19F (27–28 Hz).
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 81 No. 12 2011